This proposal is designed to investigate the acute effects of insulin upon the ubiquitin-proteasome pathway. Insulin is known to decrease release of amino acids from muscle by decreasing protein breakdown. A candidate for the site of insulin~s action is the ubiquiin- proteasome pathway which appears to be the major pathway of proteolysis in most cells Protein breakdown is accelerated in diabetes. This is clinically significant because the amino acids released serve a s gluconeogenic substrates which serve to worsen the hyperglycemia. In addition, accelerated protein breakdown can lead to muscle wasting. Identification of the pathway of protein breakdown in diabetes could lead to the development of specific therapeutic interventions. The first specific aim is to investigate whether insulin acutely regulates the ubiquitin-proteasome pathway in muscle. This will be determined by incubating isolated muscles from normal rats in the presence of insulin, lactacystin (an inhibitor of proteasome), and a combination of the two. The second specific aim is to investigate whether diabetes increases the activity of the ubiquitin-proteasome pathway and if insulin acutely inhibits this pathway. This will be accomplished by incubating muscles from diabetic animals in the presence of insulin. In addition proteasome activity upon a fluorogenic substrate will be measured after giving insulin in vivio to diabetic rats.